Stabilization of hydrocracked lube oil by contacting said oil with a catalyst of the zsm-5 type

ABSTRACT

A process for stabilizing a hydrocracked lube oil against deterioration attributable to exposure to light and/or air by contacting such hydrocracked lube oil containing a substantial proportion of paraffins with a catalyst of the ZSM-5 type under specified conditions.

United States Patent [191 Espenscheid et al.

Filed:

STABILIZATION OF HYDROCRACKED LUBE OIL BY CONTACTING SAID OIL WITH A CATALYST OF THE ZSM-S TYPE Inventors: Wilton F. Espenscheid, Princeton; Tsoung Y. Yan, Trenton, both of NJ.

Mobil Oil Corporation, New York, NY.

July 6, 1973 Appl. No.: 377,003

Assignee:

US. Cl. 208/307, 208/264 rm. Cl Cl0g 23/04 Field of Search 208/307, 264, 211, 212,

References Cited UNITED STATES PATENTS 10/1959 Carters 208/264 Primary Examiner-Delbert E. Gantz Assistant ExaminerJuanita M. Nelson Attorney, Agent, or Firm-Andrew L. Gaboriault; Raymond W. Barclay A process for stabilizing a hydrocracked lube oil against deterioration attributable to exposure to light and/or air by contacting such hydrocracked lube oil containing a substantial proportion of paraffins with a catalyst of the ZSM-5 type under specified conditions.

ABSTRACT 7 Claims, No Drawings STABILIZATION or I-IYDROCRACKED LUBE on. BY coNTAg q s A II) OI-L WITH A CATALYST OF THE zsM-s TYI IF BACKGROUND or THE INVENTION 1. Field of the Invention This invention relates to a process for catalytically stabilizing hydrocracked lube oils. More specifically, the present invention is concerned with stabilization of hydrocracked lube oils against deterioration upon exposure to light and/or air.

2. Description of the Prior Art Lubricating oils, i.e., hydrocarbon materials boiling above 650F., have been produced by distillation of a crude oil, followed by solvent refining, solvent dewaxing, acid treating and clay percolation. Acid treating in such sequence of operations has been employed to improve color and resistance to oxidation of the oils.

Lubricating oils have also been obtained in processes wherein a mild hydrotreating or hydrofinishing step has been substituted for solvent refining, acid treating and- /or clay percolation. Hydrotreating or hydrofinishing involves contacting with hydrogen in the presence of a hydrogenating catalyst under essentially non-cracking conditions to convert contaminants in the crude distillate to easily removable or harmless species.

More recently, lubricating oils have been produced by hydrocracking. In this process, a heavy petroleum oil is contacted with hydrogen at elevated temperature and pressure in the presence of a hydrocracking catalyst. The hydrocracked product is separated into materials boiling in different temperature ranges, including the lubricating oil range, i.e., oils boiling above 650F.

Lubricating oils produced by hydrocracking unfortunately suffer from the shortcoming that they are not completely stable when exposed to light and air. When so exposed, sediment and lacquer formation occurs,

thus lessening the commercial value of such lubricants. 40

The present invention is directed to a process for overcoming such shortcoming and stabilizing the hydrocracked lube oil product.

SUMMARY OF THE INVENTION ence of a small amount, generally at least about 1 50 weight percent, of paraffins capable of entering the pore structure of the catalyst employed. Such paraffins include normal paraffins and those having slightly branched chains, i.e., those paraffins characterized by a maximum cross-sectional dimension of not more than 55 approximately 7.1 Angstroms and may be added from an outside source to the hydrocracked lube oil or inherently contained in a waxy hydrocracked lube. Contact is effected in the presence of a catalyst selected from the group consisting of( l) HZSM5 and (2) dealuminized mordenite having a silica/alumina ratio in the range of m 200 at a temperature within the approximate range of 400 to 650F., a liquid hourly space velocity of 0.1 to 10, a pressure from about atmospheric to 2,000 psig, in the presence or absence of hydrogen, and recovering from said contacting a lubricating oil of improved stability characteristics.

DESCRIPTION OF SPECIFIC EMBODIMENTS The hydrocracked lube feed is obtained by hydrocracking of hydrocarbon feed material which boils above about 650F. and includes stocks such as heavy gas oils, residual stocks, propane deasphalted raffinate, top crudes, cycle stocks, reduced crudes, as well as high boiling hydrocarbon fractions of cracking derived from coal, tars, pitches, asphalts and shale oils.

Such hydrocarbon feed is contacted in the presence of a hydrocracking catalyst composed of a component having cracking activity in combination with a hydrogenation component. These catalysts are well known in the art and include oxides and sulfides of metals of Groups VI and VIII such as for example chromium sulfide, molybdenum sulfide, tungsten sulfideas well as the sulfides of iron, cobalt, nickel, palladium, platinum, rhodium, osmium and iridium. Other hydrocracking catalysts include mixtures of the above oxides and sulfides of metals of Groups VI and VIII such as mixtures of nickel sulfide and tungsten sulfide; cobalt sulfide and molybdenum sulfide; and nickel sulfide and molybdenum sulfide. The oxides and/or sulfides of the specified metals may be deposited upon adsorbent supports such as alumina, silica/alumina or silica-zirconia. Particularly preferred catalysts include those comprising at least one of the metals mentioned above deposited on a composite of oxides of at least two elements of Groups IIA, IIIB, IVA and IVB of the Periodic Table. Typical of such preferred catalyst is a sulfide or unsulfided composite containing 1 to 8 weight percent of cobalt oxide and 3 to 20 weight percent of molybdenum trioxide deposited on a silica/alumina or silicazirconia base.

Hydrocracking in the presence of the above-noted catalyst is carried out in the presence of hydrogen. Either pure hydrogen may be used or hydrogen rich gases of varying purity, such as obtained from reforming, may be used. The hydrogen rich gas is generally circulated in the hydrocracking operation at a rate in the range of from about l,000 to about 20,000 standard cubic feet of hydrocarbon charge and preferably from 3,000 to 10,000 s.c.f. per barrel of charge. The hydrocarbon charge is contacted, together with hydrogen, with a hydrocracking catalyst of the type described above at a temperature within the range of from about 500F. to about l,000F., preferably 600F. to 850F. Hydrogen pressure is selected from within the range of from about 500 to 10,000 pounds per square inch gauge (p.s.i.g.) and preferably at least about 1,500 p. s.i.g. The liquid hourly space velocity (L.H.S.V.) of charge normally falls within the range of 0.1 to 10 and preferably 0.2 to 3 volumes of charge (as F. liquid) per volume of catalyst per hour.

The products of hydrocracking are withdrawn and cooled to a temperature at which hydrogen-rich gas is separated from the normally liquid product. The latter is then passed to a fractionator from which several different boiling range fractions including gasoline, kerosene and lube oils are removed. A lubricating oil fraction boiling above about 650F. constitutes one of the recovered fractions. This fraction is either treated directly, as described above, or first dewaxed by any suitable convenient means and then subjected to the described stabilizing treatment. A

The catalysts used herein for effecting stabilization of hydrocracked lube oils are preferably those of the ZSM-S type. Such catalysts comprise a ZSM-5 type crystalline zeolite in desired cationic form. Crystalline zeolite ZSM5 and its method of preparation are more particularly described in U.S. Pat. No. 3.702.886, the disclosure of which is incorporated herein by reference. A particularly effective catalyst is one of the ZSM-5 type wherein the initial sodium cations have been replaced with hydrogen ions, either as a result of treatment with an acid or as a result of replacement of the original sodium cations with ammonium cations which upon heating are converted to hydrogen cations. The ZSM-5 zeolite in desired cation form, such as HZSM-S, may be used as such or in combination with another material resistant to the temperatures and conditions employed in the conversion process. Such materials include active and inactive materials and synthetic or naturally occurring materials such as clays, silica and/or metal oxides. A particular feasible composite is one containing HZSM5 in combination with an alumina binder.

In addition to catalyst comprising a zeolite of the ZSM5 type, it has also been established that other high silica/alumina ratio crystalline aluminosilicates may be employed, such as for example dealuminized mordenite having a silica/alumina ratio of l5 to 200. The dealuminized mordenite may-be obtained by treatment of natural or synthetic mordenite having a silica/alumina ratio of approximately by exposing the same to treatment with EDTA (ethylene diamine tetraacetic acid) or other suitable extractant for alumina in accordance with well known techniques to yield a resulting mordenite product having a portion of its original alumina removed so that the dealuminized mordenite has a silica/alumina ratio in the above speci fied range.

The hydrocracked lube oil undergoing stabilization treatment is, in accordance with the present invention,

. brought into contact with the above-described catalyst in the presence of at least about l weight percent and generally not more than about 10 weight percent of paraffin hydrocarbons which are capable of entering the pore structure of such catalyst. The latter may be either introduced into the hydrocracked lube from an external source to bring the paraffin content up to a minimum of about 1 weight percent, particularly in those instances wherein the initially obtained lube oil fraction has been subjected to dewaxing. Normal or slightly branched paraffins contemplated for addition include those in the C to C range and preferably those in the C to C30 range including mixtures of such paraffins with one another. Alternatively. a waxy hydrocracked lube oil fraction. which has not undergone previous dewaxing or which has undergone partial dewaxing and which contains at least about 1 weight percent of the above-designated paraffms. may be used without the addition of supplemental paraffins. [t is, however, an essential feature of the present process that contact of the hydrocracked lube with the above catalyst be effected in the presence of at least about i weight percent and generally not more than about 10 weight percent of paraftins capable of entering the pore structure of the specified catalyst.

Contact of the hydrocracked lube oil containing the noted paraffins with the above-described catalyst is accomplished at a temperature within the approximate range of 400F. to 650F. and preferably between about 450F. and 550F. at a liquid hourly space velocity of 0. l to 10. at a pressure of from about atmospheric to about 2,000 p.s.i.g., either in the presence or absence of hydrogen. When hydrogen is used, the resulting product has been found to have an improved color as well as being stabilized with respect to light and/or air as compared with a similar operation in which hydrogen is not present. When employed, hydrogen may be used up to pressures of about 2,000 p.s.i.g. As above noted, the liquid hourly space velocity may be in the range of 0.1 to E0. Preferably the liquid hourly space velocity of the hydrocracked lube oil undergoing stabilization is within the approximate range of 0.3 to 3 volumes of charge per volume of catalyst per hour. It is generally preferred to employ relatively high space velocities for the purpose of minimizing cracking to products boiling below 650F.

After the above-described contact of the hydrocracked lube oil in the presence of the specified paraffins with the particular crystalline aluminosilicate catalyst under the recited conditions. a lube oil product is recovered by removal from the solid catalyst by feasible means such as filtration followed by distillation to remove light ends. The product so obtained is significantly more stable to light andfor air than the untreated hydrocracked lube oil.

The following examples will serve to illustrate the process of the invention without limiting the same.

EXAMPLE 1 A hydrocracking feed made up of a mixture of ap proximately equal parts by weight of heavy vacuum gas oil and propane deasphalted raffinate was hydrocracked in the presence of a nickel tungsten sulfide on silica-zirconia catalyst at a temperature of 725F., 0.5 LHSV and 2,500 p.s.i.g. pressure.

The resulting product was distilled to remove the fraction boiling below 650F. The fraction above 650F. was dewaxed by treatment with methyl ethyl ketone and cooled to yield a hydrocracked lube oil.

To the above hyrocracked lube oil was added 7 weight percent of n-hexadecane. The resulting mixture was contacted with an extruded catalyst containing percent HZSM5 and 35 percent alumina binder in a batch reactor at a catalyst/oil of 0.02, a temperature of 450 to 550F. and 0 p.s.i.g. for 15 hours. The resulting product was a pale yellow oil which was stable to 200 hours in an accelerated light and air degradation test. Such test involved placing ice of the oil in a small vial, capped lightly, and placed in a Rayonet Photochemical Reactor containing a 2537A ultra violet light source. The sample was inspected periodically until sludge formation occurs. The untreated oil subjected to such test became dark amber and deposited heavy sediment after 40 hours.

EXAMPLE 2 A sample of hydrocracked lube oil characterized by a viscosity of 250 Saybolt Universal Seconds at l00F was passed over hydrogen mordenite (SiO /Al O of 98) at 500F.. atmospheric pressure and a LHSV of 0.4.

The product was topped to remove light ends and tested for light/oxidative stability as described in Example l. The following table shows the stability of the untreated oil and the dealuminized mordenite treated oil.

Catalyst Reaction LHSV Stability/Hrs.

Temp. F.

None 50 H mordenite (SiO,/Al,0:=98) 500 0.4 H58 EXAMPLE 3 Dewaxed hydrocracked lube oil containing 7 weight percent of n-hexadecane prepared as in Example 1 was contacted with a fixed bed containing either 1 or 3 cc of a catalyst of HZSM-S obtained by extruding the ammonium form of ZSM-5 (65 weight percent), with alumina (35 weight percent). The resulting dried extrudate was calcined at a rate of one degree Centigrade/minute over a temperature range of 25 to 538C. and held at the latter temperature for 8 hours. The hydrocracked lube oil was passed over the catalyst at lcc/hour, atmospheric pressure and 400 to 550F. in the liquid phase. The product was vacuum-topped at 450F. and -25 inches vacuum to remove the light ends. The topped products were tested for oxidative/- light stability as in Example 1 with the results shown in the following table:

Operating Conditions Testing Results Temp. "F LHSV Stability, Hr. Light Ends Wt. 7:

400 A 214 3 500 Va 418 17 550 '15 72 32 450 l 44 3 500 l 202 7 Feed Stock 40 It will be seen from the above that stability of the feed stock was effectively achieved over a temperature range of 400 to 500F. Operation at a higher temperature, e.g., 550F. resulted in a product of lower stabil- 'iity.

Temp. F. Stabihty. Hr. Light 'Ehdsfwi 7;

450 50m 5 500 500+ 13 550 575+ Feed 40 LII EXAMPLE 5 A waxy hydrocracked lube oil, as described in Example 4, containing approximately 20 weight percent of normal and slightly branched paraffins was contacted with the HZSM5 catalyst extrudate of Example 3 at a temperature of 500F., a liquid hourly space velocity of 0.35 and at a hydrogen pressure of0 p.s.i.g. and 350 p.s.i.g. The resulting product was tested for stability as described in Example 1 and also for color as determined by optical density using a light source having a wave length of 5,460A.

The results of such stabilization and decolorization are shown in the following table:

It will be seen from the above that the utilization of hydrogen pressure during the treating operation resulted in a product of lighter color in addition to stabilization.

It is to be understood that the foregoing description is merely illustrative of preferred embodiments of the invention of which many variations may be made by those skilled in the art within the scope of the following claims without departing from the spirit thereof.

We claim:

1. A process for stabilizing a hydrocracked lube oil against deterioration attributable to exposure to light and/or air which comprises contacting a hydrocracked lube oil with a catalyst of the ZSM5 type, in the presence of a small amount, generally at least about 1 weight percent of paraffins, which are normal paraffins or those having slightly branched chains, capable of entering the pore structure of said catalyst, said contacting taking place at a temperature in the approximate range of 400 to 650F., a liquid hourly space velocity of 0.] to 10 and a pressure from about atomospheric to 2,000 psig and recovering a lubricating oil of improved stability characteristics. I

2. The process of claim 1 wherein-said contacting is conducted in the presence of hydrogen.

3. The process of claim 1 wherein said hydrocracked lube oil is a waxy hydrocracked lube oil and said paraffins are contained therein.

4. The process of claim 1 wherein said paraffins are added to the hydrocracked lube oil.

5. The process of. claim 1 wherein said catalyst is HZSM-S.

6. The process of claim 1 wherein said temperature is between about 450F. and about 550F.

7. The process of claim 1 wherein said catalyst of the ZSM5 type is combined with a binder. 

1. A PROCESS FOR STABILIZING A HYDROCRACKED LUBE OIL AGAINST DETERIORATION ATTRIBUTABLE TO EXPOSURE TO LIGHT AND/OR AIR WHICH COMPRISES CONTACTING A HYDROCRACKED LUBE OIL WITH A CATALYST OF ZMS-5 TYPE IN THE PRESENCE OF A SMALL AMOUNT, GENERALLY AT LEAST ABOUT 1 WEIGHT PERCENT OF PARAFFINS, WHICHA RE NORMAL PARAFFINS OR THOSE HAVING SLIGHTLY BRANCHED CHAINS, CAPABLE OF ENTERING THE PORE STRUCTURE OF SAID CATALYST, SAID CONTACTING TAKING PLACE AT A TEMPERATURE IN THE APPROXIMATE RANGE OF 400* TO 650*F. A LIQUID HOURLY SPACE VELOCITY OF 0.1 TO 10 AND A PRESSURE FROM ABOUT ATOMOSPHERIC TO 2,000 PSIG AND RECOVERING A LUBRICATING OIL OF IMPROVED STABILITY CHARACTERISTICS.
 2. The process of claim 1 wherein said contacting is conducted in the presence of hydrogen.
 3. The process of claim 1 wherein said hydrocracked lube oil is a waxy hydrocracked lube oil and said parafFins are contained therein.
 4. The process of claim 1 wherein said paraffins are added to the hydrocracked lube oil.
 5. The process of claim 1 wherein said catalyst is HZSM-5.
 6. The process of claim 1 wherein said temperature is between about 450*F. and about 550*F.
 7. The process of claim 1 wherein said catalyst of the ZSM-5 type is combined with a binder. 